HDevelop User's Manual

4 CHAPTER 1. INTRODUCING HDEVELOP
Using this selection box, you are able to search images rapidly without knowing their exact file
names. In contrast to the two other possibilities, the parameters of operator Ö Ñ are
specified automatically. Thus, an explicit input of path and file name is not necessary in this
case. An icon with an appropriate variable name is created in the iconic variable area of the
variable window. Double-clicking on such an icon displays its contents in the currently active
graphics window. Figure 1.1 shows a complete configuration of HDevelop for the explained
scenario. In addition, a new window is opened — after closing the default window — to display
the image in its original size.
If you look closer at the image in figure 1.1 you will see the typical temporal offset between two
half images that occurs when taking images with a video camera. This temporal offset is 20 ms
for PAL systems and 16.6 ms for NTSC systems. HALCON offers an algorithm that computes
an interpolated full image from such a video image. The name of the appropriate operator is
ÐÐ ÒØÖÐ (see the HALCON Reference Manual). The next step is to specify this name
in the operator window’s operator name field. If it is indicated completely, HDevelop shows the
operator immediately in the operator window. Now you have to specify the variable name of
your image. For this you put in the name Ö×ØÓ in the parameter field ÁÑÑÖ. Todo
so you have two possibilities:
¯ Direct input via the keyboard.
¯ Using the combo box that is associated with the parameter text field, you may choose an
appropriate name.
The system’s suggestion for the interpolated image is ÁÑÐÐ. By clicking button ÇÃ
you insert this operator into the program and execute it immediately. The computed image is
displayed automatically in the active graphics window.
In the next step you try to separate bright from dark pixels in the image using a thresholding
operation. In this case, a segmentation using the simple thresholding operator ØÖ×ÓÐ
does not result in a satisfying output. Hence you have to use the dynamic thresholding operator
ÝÒ ØÖ×ÓÐ. For execution you need the original image (i.e., the interpolated full
image) and an image to compare (containing the thresholds). You obtain this image by using
the smoothing filter, e.g., ÑÒ Ñ. As input image you choose your original image
ÁÑÐÐ. After estimating the marks’ size in pixels, you specify a filter size which
is approximately twice the marks’ size (compare the HALCON Reference Manual entry for
ÝÒ ØÖ×ÓÐ).
To choose the operator ÑÒ Ñ, you traverse the menu hierarchy ÇÔÖØÓÖ× º ÐØÖ º
ËÑÓÓØÒ º ÑÒ Ñ. It will be displayed in the operator window immediately. Now you
specify the image variable names ÁÑÐÐ in the text field called ÁÑ and ÁÑÅÒ
in the output text field. The filter matrix size is chosen by opening the combo boxes of the
corresponding text fields (Å×Ïظ Å×ÀØ). These combo boxes contain a selection
of reasonable input values which is offered by HDevelop. In our example the size is set to 29
(see figure 1.2).
By clicking the button ÇÃ you insert the operator ÑÒ Ñ in the program and execute it.
Now you have to search for the name of the dynamic thresholding. For this you specify a
substring that is included in the operator name in the operator window’s operator name text field.
Three letters are already sufficient to produce a result. You will notice the open combo box that
presents all HALCON and/or HDevelop operators containing the first three specified letters.
HDevelop / 2000-11-16